Relax yaml parsing in releases/view page

[migmartri]

@stormmore reported that Kubeapps was failing to show the resources part of his chart.

The research showed that the root cause was a parsing error on our client.

Our yaml parser complained about a duplicated tag vs Helm does not. We should look into if there is any way to make our parser less restrictive. More taking into account that a duplicated label is not per-se forbidden or discouraged by the helm linter so it might happen again.

[prydonius]

We use the safeLoad function from https://github.com/nodeca/js-yaml#safeload-string---options-, and it looks like there is an option to be compatible with the JSON.parse behaviour which explicitly says "If true, then duplicate keys in a mapping will override values rather than throwing an error." So setting this to true should fix the reported issue, but we may want to also consider the non-safe load function as we know that Helm & Kubernetes have pre-validated the YAML we're reading. That said, I don't think we need the extra stuff load gives us, and compatibility with JSON.parse might be enough.

[prydonius]

For some reason, likely due to a bug in the upstream package, yaml.safeLoadAll does not seem to correctly support the json option, though yaml.safeLoad and yaml.loadAll do. Once again, given that we are only going to be parsing YAML that has already been parsed by Helm and Kubernetes, I think it is okay to switch to yaml.loadAll here, which seems to support some special JS-related YAML tags: https://github.com/nodeca/js-yaml#load-string---options-.

Filed nodeca/js-yaml#456 for the upstream issue.